Material containing a water activatable coating

ABSTRACT

A laminate and a method for making a laminate having a hidden or shielded image. The laminate includes a substrate having an first surface containing an image thereon and a polymeric film laminated to the first substrate surface overlying the image. The film contains an exposed water activatable opaque layer having a thickness ranging from about 0.60 mil to about 2.0 mil, the opaque layer including aluminum silicate and a binder. Upon wetting the opaque layer, the hidden or shielded image is revealed. The method includes a means for producing the laminate in high volumes for minimizing the production costs thereof. Upon drying the opaque layer, the image is again hidden or shielded from view. The laminate may be used multiple times without adversely affecting its ability to reveal and hide images.

FIELD OF THE INVENTION

The invention relates to a water activatable layer on a substrate, tomethods for producing a substrate containing a water activatable layerand to laminates made using a material containing a water activatablelayer.

BACKGROUND OF THE INVENTION

Relatively inexpensive novelty items containing hidden images areproduced in large quantities and are used in a variety of applicationsincluding game pieces, food packaging prizes, educational children'sbooks and the like. Many of these items contain full color hiddenimages. The images may be developed or revealed by applying a developeror solvent to the hidden image area of the object. The disadvantage ofmany of these items is that the object can only be used once, and oncethe image is revealed, the object no longer has significant appeal.Another disadvantage of such objects is that the developer or solvent isoften toxic or hazardous and thus could be dangerous when used byunsupervised children or infants.

In order to overcome the problems associated with the use of toxicdevelopers or solvents, objects containing water activatable coatingswere developed. When dry, the coatings are substantially opaque and thuseffectively hide an underlying image from view. However, upon wettingthe coating with water, the underlying image is revealed or is providedwith full vibrant color. Once the object again dries, the coatingbecomes opaque and thus again hides the image from view. While suchobjects and image developers are less toxic than the solvents anddevelopers used for other latent image objects, it is difficult toproduce such objects in a cost effective manner in quantities whichenable reasonable profits to the manufacturers and distributors thereof

Despite the advances in the art of printing hidden or latent images,there remains a need for a cost effect material and method for applyingthe material to a substance to produce vibrant full color images uponactivation.

SUMMARY OF THE INVENTION

Considering the foregoing, the present invention provides a laminatewhich includes a substrate having a first surface containing an imagethereon and a polymeric film laminated to the first substrate surfaceoverlying the image. The film contains an exposed water activatableopaque layer having a thickness ranging from about 0.60 mil to about 2.0mil wherein the opaque layer comprises aluminum silicate and a binder.

Another aspect of the invention provides a method for coating apolymeric film with a water activatable opaque layer. According to themethod, a polymeric film having a first surface and a second surface isprovided and an opaque water activatable material is applied to thefirst surface of the film using a Meyer rod coating technique. Afterapplying the material to the film, the material is dried.

Still another aspect of the invention provides a method for making anovelty item containing a water revealable image which includesproviding a porous web, printing an image on a surface of the web,applying an opaque water activatable coating to a first surface of apolymeric film by means of a Meyer rod coating technique, drying thecoating to obtain an opaque layer on the film, and laminating the filmto the porous web so that the image is between the porous web and asecond surface of the film and the opaque layer is exposed.

An important advantage of the invention is that objects containing theopaque coating may be produced in high volume using the techniquesdescribed herein. Another advantage of the invention is that the opaquecoated film may be applied to a variety of substrates containing imageswhich may be black and white or full color images. Still anotheradvantage of the invention is that the image containing substrate andfilm containing an opaque layer may be produced separately in the sameor remote locations and combined later into a single composite material.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the invention will become apparent byreference to the detailed description when considered in conjunctionwith the figures, which are not to scale, wherein like reference numbersindicate like elements through the several views, and wherein:

FIG. 1 is a cross-sectional view, not to scale, of an opaque filmmaterial according to the invention;

FIG. 2 is a cross-sectional view, not to scale, of a substratecontaining an opaque film material according to the invention;

FIG. 3 is a simplified schematic for a process for making novelty itemsaccording to the invention;

FIG. 4 is an illustration of a laminate containing images having hiddenfeatures; and

FIG. 5 is an illustration of a laminate containing images whereinpreviously hidden image features are revealed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to FIG. 1, the invention provides an opaque film material10 containing an opaque layer 12 coated onto a substantially transparentmaterial 14 as by a Meyer rod coating technique. The transparentmaterial 14 may be selected from glass, fiberglass or a flexiblepolymeric film. Preferably the transparent material is a polymer,copolymer or polyester film, most preferably a thermoplastic polymericfilm selected from the group consisting of polyethylene, polypropylene,polystyrene and polybutylene films. When a film is used as thetransparent material, the film preferably has a thickness ranging fromabout 0.5 to about 2.5 mils and is preferably substantially transparent.A particularly preferred film is an optically clear, biaxally oriented,polystyrene film available from Wausau Coating of Wausau, Wis. Thelength and width of the transparent material is not critical to theinvention and may be any suitable length and width which may be coatedusing conventional Meyer rod coating apparatus.

The term “substantially transparent” means that details of objects orimages covered by such a film are essentially visible through the filmas opposed to blocking all or a substantially portion of the object orimage from view.

An important feature of the invention is the use of an opaque coatingformulation for forming the opaque layer 12 on the transparent material14. The coating formulation includes from about 5 wt. % to about 40 wt.% aluminum silicate and from about 60 wt. % to about 95 wt. % binder.The aluminum silicate preferably has a particle size ranging from about1 micron to about 10 microns.

The binder of the coating formulation is preferably an aqueous-basedbinder containing solvent, from about 1 wt. % to about 5 wt. % butylacetate, from about 5 wt. % to about 10 wt. % ethylene glycol monobutylether (butyl CELLOSOLVE) and from about 5 wt. % to about 15 wt. %propylene glycol. A preferred binder is a water-based acrylic materialavailable from 2nd Story of Canton, Ohio under the trade name KTCcoating. The binder and aluminum silicate formulation is mixed and theviscosity of the mixture is adjusted with water to produce a coatableformulation having a viscosity within the range of from about 800 toabout 1500 centipoise. It is particularly preferred to adjust theviscosity of the formulation to provide a mixture which can be appliedby a Meyer rod coating technique. A formulation containing binder andaluminum silicate which has a viscosity suitable for applying by a Meyerrod coating technique is available from 2nd Story Concepts of Canton,Ohio under the trade name KTC60-2416H.

The transparent material 14 is preferably attached to a substrate 16containing an image to be hidden. The substrate 16 may be selected froma wide variety of materials containing an image, including, but notlimited to, paper and cellulosic webs, metals, plastics, glass, ceramicand the like. It is preferred that the substrate 16 be a relativelyporous material as compared to the porosity of transparent material 14.A particularly preferred substrate 16 is a paper web containing an imageprinted on a surface 18 thereof. The image may be printed on the surface18 by a wide variety of printing techniques including, but not limitedto, flexographic, gravure, screen and offset printing techniques.

Once the image is printed on the surface 18 of the substrate 16, theopaque film 10 is attached directly to the substrate 16 so that theprinted image on surface 18 is effectively covered or hidden by theopaque layer 12 on transparent material 14. The opaque film 10 may beattached to the substrate 16 by means of an adhesive 20 or, in the caseof a thermoplastic film used as transparent material 14, by thermallamination or cohesion techniques. A preferred adhesive is selected frompressure sensitive adhesives, emulsion acrylic and the like. In the caseof a thermoplastic film for transparent material 14, a particularlypreferred film is a biaxally oriented polystyrene having a softeningpoint in the range of from about 100° F. to about 200° F.

It is important that the coating of opaque layer 12 on the transparentmaterial 14 be of sufficient thickness to effectively hide or shield theimage on surface 18 of substrate 16 from visual perception. It is notrequired that the image be completely invisible to the unaided eye,however, detailed features of the image such as the vibrant colorthereof should be sufficiently shielded from view by the opaque layer12. In order to obtain a sufficiently hidden image on surface 18, it ispreferred to apply an opaque layer 12 to transparent material 14, theopaque layer having a thickness ranging from about 0.60 mil to about 2.0mil.

As set forth above, the opaque layer 12 is preferably applied from anaqueous mixture to the transparent layer 14 by a Meyer rod coatingtechnique. A Meyer rod coater enables high speed production of opaquelayers 10 for reduced manufacturing costs thereof. After coating thetransparent layer 14, layer 12 is dried to provide opaque film 10.Drying of layer 12 may be achieved as by use of a conventional dryingtunnel using a drying temperature in the range of from about 100° F. toabout 230° F. Because of the use of a Meyer rod coater, a continuousfilm containing opaque layer 12 may be dried at a rate of about 200 to400 feet per minute. Such a technique of coating and drying incombination provides advantageous economies of scale not heretoforeobtainable by other processing techniques. For example, application ofan opaque layer 12 directly to the printed substrate 16 requires anintermediate drying step for the printed image. Because the opaque film10 may be produced in a separate process from the printing of images onsubstrate 16 and the two components combined later, the limiting processbecomes the laminating step rather than a drying step or printing step.Lamination can typically be conducted at much higher rates than dryingprinted images.

Once the opaque layer 12 is sufficiently dry, the opaque film 10 may beattached to substrate 16 or coiled on a roll for later attachment tosubstrate 16 at a remote location. A particularly preferred process forforming a composite material containing an image hidden or shielded byopaque film 10 is illustrated schematically in FIG. 3. A transparent,flexible film 30 is provided by supply reel 32 to a Meyer rod coater 34containing a supply of aqueous opaque material 36 for applying to onesurface of film 30 to provide coated film 38. The coated film 38 is thendried by passing film 38 through a tunnel dryer 40, preferably at a rateof from about 200 to about 400 feet per minute and at a temperatureranging from about 250° to about 350° F. The resulting opaque film 42may be re-rolled on a storage roll for lamination to a substrate at aremote location or is preferably laminated in-line to a substrate. Film30 may include an adhesive layer on surface 44 thereof or an adhesivelayer may be applied to surface 44 thereof before or after coating film30 with opaque material 36. In the case of a thermoplastic film 30, theopaque film 42 may be directly laminated to a substrate web by a heatlamination technique.

In the case of a continuous process for producing a composite web havinga hidden image, a porous substrate, preferably a paper web 46 isprovided by supply reel 48 to a printing apparatus 50 such as aflexographic, gravure, lithographic or screen printer which applies animage to surface 52 of web 46. The image containing web 54 may then belaminated to opaque film 42 as described above using laminator 56 whichmay be pressure rolls or heated pressure rolls and the like. Theresulting composite web 58 contains an image covered or hidden by opaquefilm 42.

Upon wetting surface 60 (FIG. 2) of composite web 58, features of theimage become visible to the unaided eye. Such features may includedetailed lines or additional printed images, vibrant colors and thelike. The features hidden from view by the opaque layer 12 according tothe invention may be seen by comparing the images of FIG. 4 with theimages of FIG. 5. Upon wetting the opaque layer 12, features such aslines and colors 62 in images 64 may be clearly seen. Upon drying, thelines and colors are again effectively hidden from view as shown in FIG.4. The composite web 58 may therefore be used multiple times withoutadversely affecting subsequent image development by wetting opaque layer12.

As also seen in FIG. 4, the opaque layer 12 may also contain indicia,lines or images 66 which are visible without wetting layer 12. Theseprinted indicia, lines or images 66 may be enhanced by the underlyinghidden color or images or may be used merely to indicate the location ofthe hidden images.

While the invention has been described in detail, it is to be expresslyunderstood that various changes of form, design or arrangement may bemade to the invention by those skilled in the relevant art withoutdeparting from the spirit and scope of the invention. Therefore, theabove mentioned description is to be considered exemplary, rather thanlimiting, and the scope of the invention is defined by the followingclaims.

What is claimed is:
 1. A laminate comprising a substrate having a firstsubstrate surface containing an image thereon and a polymeric filmlaminated to said first substrate surface overlying said image, saidfilm containing an exposed water activatable opaque layer having athickness ranging from about 0.6 mil to about 2.0 mil, said opaque layerderived from a coating formulation comprising from about 5 to about 40wt. % aluminum silicate and from about 60 to about 95 wt. % binder,wherein the binder comprises a mixture of solvent, butyl acetate,ethylene glycol monobutyl ether and propylene glycol.
 2. The laminate ofclaim 1 wherein the substrate comprises a porous substrate.
 3. Thelaminate of claim 2 wherein the substrate comprises natural or syntheticpaper.
 4. The laminate of claim 1 wherein the polymer of the polymericfilm is selected from the group consisting of polyethylene,polypropylene, polystyrene and polyester.
 5. The laminate of claim 1wherein the opaque layer comprises a layer applied to the polymeric filmby a Meyer rod coating technique.
 6. A method for coating a polymericfilm with a water activatable opaque layer comprising providing apolymeric film having a first surface and a second surface, applying anopaque water activatable material containing from about 5 to about 40wt. % pigment and from about 60 to about 95 wt. % binder to the firstsurface of the film using a Meyer rod coating technique and drying thewater activatable material to provide a single water activatable opaquelayer having a thickness ranging from about 0.60 mil to about 2.0 mil,wherein the binder comprises a mixture of solvent, butyl acetate,ethylene glycol monobutyl ether and propylene glycol.
 7. The method ofclaim 6 wherein the water activatable material comprises a mixture ofaluminum silicate and binder, the mixture having a viscosity rangingfrom about 800 centipoise to about 1500 centipoise.
 8. The method ofclaim 6 wherein the polymer of the polymeric film is selected from thegroup consisting of polyethylene, polystyrene, polypropylene andpolyester.
 9. The method of claim 6 wherein the second surface of thepolymeric film contains an adhesive layer, and the method furthercomprises the step of applying the polymeric film to a substrate withthe adhesive.
 10. The method of claim 9 wherein the substrate containsan image thereon and the film is applied to the substrate in a mannersufficient to effectively cover the image and limit visual perceptionthereof.
 11. The method of claim 10 wherein the substrate comprises aporous substrate.
 12. The method of claim 6 wherein the polymeric filmis a thermoplastic film, further comprising cohesively bonding thepolymeric film to a substrate by a heat lamination process.
 13. Themethod of claim 12 wherein the substrate comprises a porous substrate.14. A method for making a novelty item containing a water revealableimage, the method comprises the steps of providing a porous web,printing an image on a surface of the web, applying an opaque wateractivatable coating containing from about 5 to about 40 wt. % pigmentand from about 60 to about 95 wt. % binder to a first surface of apolymeric film by means of a Meyer rod coating technique, wherein thebinder comprises a mixture of solvent, butyl acetate, ethylene glycolmonobutyl ether and propylene glycol, drying the coating to obtain anopaque layer on the film to provide a single water activatable opaquelayer having a thickness ranging from about 0.60 mil to about 2.0 mil,and laminating the film to the porous web so that the image is betweenthe porous web and a second surface of the film and the opaque layer isexposed.
 15. The method of claim 6 wherein the water activatablematerial comprises a mixture of aluminum silicate and binder, themixture having a viscosity ranging from about 800 centipoise to about1500 centipoise.
 16. The method of claim 14 wherein the polymer of thepolymeric film is selected from the group consisting of polyethylene,polypropylene, polystyrene and polyester.
 17. The method of claim 14wherein the second surface of the polymeric film contains an adhesivelayer.
 18. The method of claim 14 wherein the polymeric film is athermoplastic film and the film and web are laminated by heating thefilm to a temperature sufficient to form a cohesive bond between thefilm and web.